AFAIK it's where you go to view other people's miis that you have not as of yet got in your plaza (where the miis of your console are). To enable other people to view your miis they have to have 'mingle' selected when you were creating them and also in the parade alow them to travel.

mat, click the link in my signature and it will take you to an updated Wii Family list.

In regards to your question, on the main Wii menu click on the bottom right hand envelope where your messages would normally be, once in there, bottom left is an address book. The first page will tell you your Wii address.
HTH